If you go to high altitude quickly, your body has to adapt to the thinner air and the lack of oxygen. Two important things happen almost immediately:
you breathe faster and more deeply to maximise the amount of oxygen that can get into the blood from the lungs, and your heart pumps more blood to increase the supply of oxygen to your brain and muscles
You can demonstrate how important breathing harder is by using our high altitude oxygen calculator. Some people include breathlessness during exercise as a component of altitude sickness, but this is misleading. Breathing harder is a normal response to the shortage of oxygen, but it does have other effects on the body: click to learn more about breathing at altitude.
The sensation of breathlessness usually indicates that the lungs are having difficulty in supplying the body’s demand for oxygen. Therefore, if a climber is walking too fast for his lungs to keep up, he feels breathless and slows down. However, breathlessness at rest indicates that the lungs are having difficulty in supplying even the small amount of oxygen that the body needs when it is resting. This is an ominous sign at high altitude and may indicate the development of high altitude pulmonary oedema (HAPE). Any climber who is breathless at rest at high altitude should descend to a safer altitude as soon as possible. If you have had HAPE, please register with the online HAPE database.